The present invention relates to a cardiac pacemaker and, more particularly, to a cardiac pacemaker which is improved to avoid any feel of constraint of the patient.
A cardiac pacemaker is a device which detects cardiac information and which imparts stimulation to heart based on the cardiac information to control the pacing of the heart. In recent years, improvements have been made in the field of cardiac pacemaker such as reduction in the size and weight of the pacemaker, prolongation of the life of the battery, improvement in the lead electrodes and so forth, as well as novel functions such as a programmable function which enables extra-body adjustment of the pacing conditions and physiological pacing function which can be incorporated in the pacemaker. Thus, nowadays, cardiac pacemaker as an artificial organ has been developed to a considerably high level of perfection. These improvements also permit safe and easy operation for imbedding. It is to be noted, however, a greatest difficulty is encountered in bringing and keeping the lead electrodes with the endocardium. It is very important that the lead electrodes are securely mounted in proper positions. In some cases, a plurality of lead electrodes are mounted in atrium and ventricle. In most cases, it is not easy to demount the lead electrodes once these electrodes are mounted. Thus, the lead wires are often left in the patient's body, in particular in the heart or blood vessel, even after they have become inoperative due to cutting or due to calcification of the ends of the lead electrodes.
FIG. 12 illustrates a known cardiac pacemaker. The cardiac pacemaker 300 has a main body 340, lead wires 350 and lead electrodes 355 for delivering the stimulating pulses to the cardiac muscle. This known cardiac pacemaker, however, suffers from the following disadvantage due to the fact that the main body 340 and the stimulating electrodes 355 are connected through lead lines 350.
First problem
Mal-function of the pacemaker tends to be caused by inferior sealing in the region 320 where the main body 340 is connected to the lead lines. Such inferior sealing is a problem also from the view point of safety in electricity.
Second problem
In order to ensure that the connecting region 320 is sealed without fail, the connecting region 320 inevitably occupies a large portion, e.g., 1/4 or so in volume, which seriously impedes reduction in the weight and size of the main body 340.
Third problem
In some cases, the lead lines 350 are too long to fit on the patient's body. Any surplus portion of the lead lines 350 is wound on the main body 340. Consequently, it is necessary to preserve, in the thorax, a space of a volume greater than that required for imbedding the main body 340.
Fourth problem
Problems are still encountered that the risk of pacing failure due to cutting of the lead line 350 and difficulty in taking the inoperative lead lines out of the patient's body.
Fifth problem
Blocking in a blood vessel or pressurizing of the blood vessel may dangerously occur particularly when the patient is an aged person.